Direct Current (herein “DC”) is required for a wide variety of electronics and equipment. Typically, one uses a transformer to convert alternating current (herein “AC”) power to DC which is inefficient. Or, even if using a DC power source, such as a solar panel/photo-voltaic input (herein, “PV), one converts this power to AC and then back to DC. In still other versions of prior art systems, there is DC input and DC output with a battery there-between and/or voltage conversion.
Each of these involves inefficiencies, but is typically required because the power source at one's disposal is either AC or unstable. That is, when using a PV panel for power, the output is usually unstable because of the reliance on energy from the sun, the amount which reaches the panel changing throughout the day and being all but practically non-existent at night.
FIG. 1 shows a prior art power conversion device with a photovoltaic inverter. Within the inverter is a DC/DC pre-conditioner and a DC/AC inverter. In this case, the load interfaces with an AC power grid (source of power provided as AC current from outside a physical location or address where the power is being used). The power sink (the device that utilizes the current to perform an action) receives only AC power with no detectable PV or DC input at the point on a circuit or bus where the power sink is located. The conversion loss of PV power includes DC/DC loss and DC/AC inversion loss. About 40% of power loss is due to the DC/DC loss and 60% due to the DC/AC inversion.
FIG. 2 shows a prior art photovoltaic charging system. The charger has a DC/DC pre-conditioner and a DC/DC charger. The interface between the battery and load might have a battery controller as well. For simple applications, the load can connect to the battery directly. For more complex systems, a battery controller (a device which controls when current is drawn from the battery and placed into the bus, alone or in addition to existing current) is needed. In this case, the load interfaces with the battery, and the PV power source is undetectable within the circuit at the point of the load. (“Load”, “power load”, “sink”, and “power sink” are used interchangeably in this disclosure, the definition being provided above with respect to FIG. 1.) The conversion loss of PV power in this case includes both DC/DC loss and DC/DC charger loss. Each contributes to about 50% of the power loss.
While these prior art systems overcome the problem of incorporating and being able to use a PV power output to power a device, they are inefficient. What is needed is a way to more efficiently use an unstable power source.